Speculation on Mars Life Increases After Discovery of Bacteria That Photosynthesizes Without Sunlight

Photosynthesis, according to every grade school science teacher ever, is the process plants and other organisms use to convert light energy into chemical energy. Sunlight is a pretty important part of the equation, or at least that's what a group of researchers thought before they discovered cyanobacteria living in rocks thousands of feet below the Earth's surface in an abandoned mine in Spain. The discovery raises further questions about the possibility of life beneath the surface of Mars and other planets.

In new research published in the journal Proceedings of the National Academy of Sciences, the international team of scientists led by Fernando Puente-Sánchez from the Spanish Centre of Astrobiology in Madrid described the process of drilling over 2,000 feet into the rock to collect samples. A closer look into the samples revealed different kinds of bacteria, some of which should only exist in places where the light touches. "Cyanobacteria are ecologically versatile microorganisms inhabiting most environments, ranging from marine systems to arid deserts," Puente-Sánchez and his co-authors wrote. "Although they possess several pathways for light-independent energy generation, until now their ecological range appeared to be restricted to environments with at least occasional exposure to sunlight."

Gizmodo reports that through genetic analyses, the researchers learned that in lieu of sunlight, the cyanobacteria found in the cave could produce enzymes that turn hydrogen gas into useful energy. In explaining how that could be possible, the scientists chalk it up to the resilience of the bacteria and something deep in its evolutionary lineage. "Endolithic cyanobacteria are perfect candidates for inhabiting the deep subsurface, as they are already adapted to living inside rocks and are able to withstand severe nutritional and environmental stresses and experience periodic anoxia during the diel cycle. Further, some cave-dwelling cyanobacteria survive for long periods in the near-total absence of light, where photosynthesis is no longer possible...they possess several defense mechanisms that, having likely evolved to cope with light stress and desiccation in their original habitats, could also be triggered under the reducing conditions found in the deep subsurface and result in functional electron transport chains."

If signs of life can be found thousands of feet below us, is it plausible that if we dig a little deeper (literally) on other planets, similar discoveries could be made? What alien bacteria is lurking in space rocks snacking on hydrogen or some other substance while we are studying surface samples and coming up empty?